How do disc injuries cause back pain?
An injury to the disc can cause pain in several ways. First, the injured disc can be painful just by tearing the outer portion of the disc and irritating the nerves that innervate the outer edge of the disc. Secondly, the injured disc may begin to degenerate, causing enzymes to be produced. These enzymes can leak out of the disc and further irritate the nerves on the outside of the disc. This is a common cause of chronic back pain. Third, the injured disc is often weakened and does not function properly. Specifically, it does not prevent abnormal motion of one vertebra in relation to the next. For example, if a knee ligament or shoulder ligament were injured and stretched, the individual would lose support in that knee or shoulder. The same happens at a microscopic level in the back when a disc is injured. This allows for micro-translation movements of the disc, which causes irritation of the nerves that innervate the disc, as well as of the surrounding facet joints and supporting tiss
Injury to the disc can cause pain in three different ways. First, the injured disc can itself be painful. The damage results in development of pain coming directly from the disc. Second, the injured disc may be weakened to the point that it no longer functions as it should. Normally, the discs allow for normal movement of the spine by acting as “shock absorbers” between the blocks of bone of the spine (vertebra). When the disc fails to do its job, the other parts of the spine, such as the joints known as facet joints, may suffer. This can generate secondary pain arising from the other structures. Finally, an injured disc may be displaced from its normal position and pinch (compress) a nerve, causing pain. If the displaced disc compresses or inflames a nerve, there may be back pain, leg pain or a combination of both.
